1. Field of the Invention
This invention relates to memory storage devices using rotating disks (hereinafter referred to as "disk drives") for the storage of information in the form of magnetic bits and in particular to an air filtration system adapted for use with such disk drives.
2. Prior Art
Disk drives are well known in the prior art. Each disk drive generally contains a plurality of disks, each disk having two surfaces. Information is stored in concentric annular tracks on the surfaces in the form of data bits. These data bits can be stored or randomly accessed while the disk rotates at high speed. Typically to store or retrieve information on a given surface, a read/write transducer or "head" having a small coil is moved across the disk surface while the disk is spinning to the data track on which the desired information is to be stored or is located. A plurality of heads (one for each disk surface) is used in each disk drive and each head rides on a thin layer of air generated by the spinning disk in close proximity to but spaced from the disk surface.
One problem with such disks is contamination. Because the head rides or "flies" within about 10 to 18 microinches of the spinning disk, any impurity of a size greater than 10 microinches will possibly jam between the head and the spinning disk causing the head to "crash". Another problem is associated with the alignment of the disks. If the disks are not properly aligned, the disk will possibly rub on the head and thereby create debris which possibly will jam between the head and the disk again causing the head to crash. To alleviate the problems of contamination and alignment, sealed disk drives have been used. These drives include read/write heads, a carriage for the heads, a drive motor and spindle, magnetic disks mounted on the spindle, and a head drive actuating mechanism located in an area adjacent to the disks to move each head across its corresponding disk surface to the proper data track on the disk, all sealed in a housing. To reduce the possibility of impurities entered the disk environment, air from the environment is filtered before being allowed into the housing and the air which flows within the housing itself due to the spinning of the disk is also filtered.
While the motor and spindle on which the disks are mounted is sealed, air leakage can occur past the seals. This leakage increases the potential for contamination of the system, particularly if the system uses impellers on the spindle to increase the air circulation within the housing.
A standard prior art air filtration system is disclosed, for example, in U.S. Pat. No. 4,282,554, issued Aug. 4, 1981 on an application of Ho, et al. In the air filtration system of Ho et al., the air to be filtered is impelled by the disk (which rotates in a counter clockwise direction when looked at from the top) into a channel or guide mounted substantially tangentially to the disk. From this channel or guide the air is driven through the filter by the high pressure generated as a result of the rotation of the disk and then through a channel back onto the disk. The typical filter used in this prior art structure has a cross-sectional area through which air can flow of about three to four square inches. One of the limitations upon the size of the housing for a disk drive is the size of the filter required to filter the air contained within the housing.